import java.io.IOException;
import java.net.*;
import java.util.Scanner;

public class UdpEchoClient {
    private DatagramSocket socket=null;
    private String serverIP;
    private int serverPort;

    public UdpEchoClient(String serverIP,int serverPort) throws SocketException {
        socket=new DatagramSocket();
        this.serverIP=serverIP;
        this.serverPort=serverPort;
    }

    public void start() throws IOException {
        System.out.println("启动客户端");
        Scanner sc=new Scanner(System.in);

        while(true){
            // 1. 从控制台读取到用户的输入.
            System.out.print("->");
            String request=sc.next();
            // 2. 构造出一个 UDP 请求, 发送给服务器.
            DatagramPacket requestPacket=new DatagramPacket(request.getBytes(), request.getBytes().length,
                    InetAddress.getByName(this.serverIP),this.serverPort);
            socket.send(requestPacket);
            // 3. 从服务器读取到响应
            DatagramPacket responsePacket=new DatagramPacket(new byte[4096],4096);
            socket.receive(responsePacket);
            String response=new String(responsePacket.getData(),0,responsePacket.getLength());
            // 4. 把响应打印到控制台上.
            System.out.println(response);
        }
    }

    public static void main(String[] args) throws IOException{
        UdpEchoClient client=new UdpEchoClient("127.0.0.1",9090);
        client.start();
    }
}
